In fact, elderly people with a network of friends or family had blood pressure similar to people who were decades younger.

The research follows hot on the heels of another study emphasising the benefits of social activity.

It showed similar survival rates for elderly people who did regular social activities rather than physical exercise.

Blood pressure

The new research, published in the Annals of Behavioural Medicine, is a study of 67 men and women, ranging in age from 20 to 70.

None had a history of heart problems or psychological disorders, such as depression.

Smokers and heavy drinkers were excluded.

Scientists from the University of Utah's Department of Psychology and Heath Psychology Program measured their blood pressure and asked them to fill in a detailed questionnaire aimed at finding out how much social support they had.

They said there was a clear relationship between increased blood pressure and age, but this only related to people who had little social support.

There was no other explanation for the difference in blood pressure, they said.

"We found that social support moderated age-related differences in blood pressure and age predicted higher resting blood pressure, but only for individuals low in social support," said Bert Uchino, who led the study.

The scientists say their findings could have important implications for preventing cardiovascular disease.

High blood pressure is one of the main risk factors for heart attacks, strokes and other cardiovascular disease.

Holistic approach

Elderly organisations say it is vital that the needs of the whole person are taken into account by policy makers.

They believe depression and mental health can play a big role in the overall health of the elderly.